This invention relates to a vibrating screed used in compacting and smoothing flowable cementitious materials. More particularly, it is concerned with a vibrating screed, which provides for improved workability and ease of use by the operator for applying vibratory compaction and leveling to flowable concrete.
Various tools are already well known in the art. At the most basic level a straight piece of lumber moved back and forth along the top of the side forms provides the leveling action. Various other devices using direct coupled gas powered vibrators as well as electric or pneumatic vibrators have been proposed. Each of these devices has some important disadvantages.
A hand-operated screed requires two laborers and demands heavy physical work. The work is both slow and requires the men to work at a low level, which is extremely hard on the lower back and knees. A hand screed also requires the concrete surface be floated and trowelled afterwards to bring the grout mixture to the surface to ready the surface for final texturing/treatment.
A number of inventions have been presented to impart vibratory force to a portable screed. This accomplishes two actionsxe2x80x94it levels the concrete by pushing the excess material in the direction of movement and also vibrates the surface of the concrete, compacting the coarse aggregate and bringing the grout to the surface resulting in a smooth surface ready for final finishing.
Vibratory screeds powered by internal combustion engines have the disadvantage that it is difficult to prevent the vibrations from the rotating eccentric weight from being transferred to both the operator and the power source itself because of the direct mechanical coupling inherent in the design of the unit. The handles and controls can be partially isolated from the vibrations but due to the direct physical presence of the drive shaft it is not possible to isolate the power source from the vibrations. As with any mechanical device, vibrations cause increase wear and accelerated breakdowns both in the power unit engine as well as in the mechanical fastenings and mounting points on the screed handle frame. As well, the rotating eccentric weight imposes heavy loads on the bearings in which it rotates, again causing heavy wear and accelerated failure. As well, the need to have the engine mounted on the back of the screed handle necessarily requires that the operator carries around and uses an awkward, difficult to handle tool that potentially imparts unsafe forces and loads on the operator""s back and back muscles. With the prevalence of lower back problems in the construction industry it is imperative that the use of awkward, heavy tools is minimized as much as possible.
Electric powered vibrators have two major problems. Firstly, a source of electric power is required. Either a generator or convenient line source is needed to power the vibrators. The portable screed must have an long power cord to connect to a suitable power source. In many instances the screeds must be used where no permanent power is available, so a portable generator must be used. In a typical sidewalk construction project the length of a day""s pour will be 600 linear feet requiring a substantial power cord or the need to move the portable generator numerous times to keep it within a convenient distance from the work area. This cord will run in and around other construction causing inconvenience and potential safety hazards (tripping, damage to finished work, physical damage to the cord itself). As well there is an increased safety hazard inherent in using electrical devices in an environment that requires the operator to be standing in water or wet material especially if the power cord is continually exposed to wear and damage as it snakes through the construction area.
Pneumatic powered vibrators have a major problem as wellxe2x80x94they require a high volume source of compressed air provided through stiff rubberized hoses. The size of the necessary compressor makes it difficult to provide a convenient portable compressed air source for continually mobile sidewalk construction. As well, the thickness of the air hoses required to provide sufficient compressed air flow makes it difficult to handle a portable screed in the limited space available for sidewalk construction. The need to have a thick, 2xe2x80x3 hose snaking through the construction area causes problems from both a work management and safety point of view.
Accordingly there has developed a need to provide a safe, easy to use means of imparting vibration to the screed that will be both durable and easy to use without negatively impacting the safety of the work place.
This invention provides a relatively light weight screed unit coupled to a portable hydraulic power pack that is carried on the back of the operator. The entire weight of the power pack unit is confined to a backpack mounted hydraulic power pack (Husqvarna 250PS or equivalent). As the waist belt and shoulder straps carry most of the weight, there is less stress on the back of the operator.
The hydraulic vibrator unit is mounted directly on the screed itself where the weight of the vibrator tends to keep the screed from floating up off the forms on the surface of the concrete. As well, this location allows for much improved isolation of the operator from the vibrations imparted to the screed. The hydraulic oil flow is transferred along relatively thin flexible hoses that do not negatively restrict use of the screed. The unit is totally self contained and the screed is dragged along the sidewalk construction as it is being used so nothing has to be moved separately as work continues. The hoses can be quickly disconnected so the unit can be stored in a relatively small space. The screed handle is mounted on a rotating hinge with a adjustment turnbuckle so that the angle of the handle to the screed can be adjusted to allow for different height operators to use the screed in comfort. Again this reduces the application of any negative stress to the lower back of the operator as he can adjust the screed handle to allow him to work in an erect stance at all times.
Thus, a primary object of the present invention is to provide a safe reliable and easy to handle mobile vibrating screed.
According to the present invention, there is provided a vibrating screed system for compacting and smoothing cementitious materials. It comprises a vibrating screed unit having a hydraulic vibrator means mounted to a frame means, a screed blade mounted to a bottom side of the frame means and a handle means mounted to the frame means by a plurality of vibration damping means and a hydraulic power pack comprising a self contained rotary power source driving a hydraulic pump. The hydraulic power pack is mounted on a back pack wearable by an operator and the hydraulic pump provides pressurized hydraulic fluid to the hydraulic vibrator means via flexible hoses.
The invention also provides a vibrating screed system comprising a vibrating screed unit and a hydraulic power pack. The vibrating screed unit comprises a hydraulic vibrator mounted to a frame, a screed blade mounted to a bottom side of the frame and a handle unit mounted at an angle to the frame by a plurality of vibration damping units. The hydraulic power pack comprises an internal combustion engine driving a hydraulic pump and is mounted on a back pack worn by an operator. The hydraulic pump provides pressurized hydraulic fluid to the hydraulic vibrator via flexible hoses.
Other objects and advantages of the present invention will become apparent from the following detailed description when viewed in conjunction with the accompanying drawings, which set forth certain embodiments of the invention.